Event-Related Potentials (ERP), particularly the P300 component, have shown potential in predicting cognitive performance. P300 latency is a reliable marker of cognitive abilities such as memory, inhibitory control, and mental efficiency, and has even been linked to personality traits. Performing cognitive tasks often involves activating specific mental processes—known as a “task set”—which are shaped by individual characteristics. However, no prior research has explored the relationship between P300 latency and performance in tasks involving task-set switching, such as a Go/No-Go task using emotional (sad) and neutral facial stimuli. This study aimed to assess whether P300 latency could predict performance in such a task that engages executive functions (EF). Results revealed a significant correlation between longer P300 latencies in posterior electrodes and correct responses in the Go condition (p < 0.001), and specifically for sad faces (p < 0.01). Notably, latencies at electrodes P3 and P4 strongly correlated with performance when both Go responses and sad face stimuli were combined (p < 0.001). A linear regression analysis using posterior P300 latencies as predictors explained 84% of the variance in correct Go responses to sad faces. These findings suggest that P300 latency may serve as a reliable predictor of EF-related task performance.